1. Field of the Invention
This invention relates generally to a battery monitor for monitoring the batteries of an electric vehicle and, more particularly, to a battery monitor that monitors the voltage and temperature of the batteries of an electric vehicle where the battery monitor is positioned proximate to the batteries.
2. Discussion of the Related Art
Today there is a growing demand for electric vehicles which run on electric power stored in multiple banks of batteries. Increased use of electric vehicles has been fueled by many factors including consumer demand, emission concerns with internal combustion engines and increased governmental regulations. Because of a number of obvious and industry related reasons, it is necessary to monitor the voltage and temperature of the batteries used by the electric vehicles.
As is well understood, it is desirable to control the charging of the batteries of an electric vehicle. To achieve the optimum and most rapid charging rate, the voltage and temperature of the batteries must be monitored to insure that the batteries do not overheat during the charging procedure. Further, it is necessary to monitor battery capacity during operation of the vehicle to determine existing battery capabilities. Conventional methods for monitoring battery voltage and temperature have several disadvantages. For example, typical battery monitoring devices for monitoring battery voltage use isolation amplifiers to isolate the battery voltage and associated current from the monitoring device. These isolation amplifiers generally use transformers, which are heavy and costly, to achieve the required isolation. Also, known monitoring devices require multiple wires attached to each battery that are routed throughout the vehicle possibly providing electromagnetic compatibility (EMC) problems with the various electrical modules used in the vehicle. In addition, some monitoring devices utilize common grounding schemes which connect the vehicle's supply voltage for its electric modules to the battery's high voltage system. Therefore, the batteries and the associated high currents are not galvanically isolated from the electric modules in the vehicle.
What is needed is a battery monitor for electric vehicles which does not suffer from the above-mentioned disadvantages. This will eliminate the use of costly transformers, reduce electromagnetic compatibility (EMC) concerns, reduce overall vehicle wiring and isolate the battery voltage and currents from the vehicles other electrical systems. It is, therefore, an object of the present invention to provide such a battery monitor for electric vehicles and a method therefore.